Radio receiver



RADIO RECEIVER Filed Sept. 24, 1950 iNVENTOR JAN VAN DER MARK- I ATTORNEY Patented Aug. 11, 1936 PATET FFICE RADIO RECEIVER Jan van der Mark, Eindhoven, Netherlands, as-

signor to Radio Corporation of America, a corporation of Delaware Application September 24, 1930, Serial No.'48d,006

, In the Netherlands October 4, 1929 6 Claims.

The present invention relates to a circuit arrangement for the detection of modulated high frequency oscillations with subsequent amplification for rendering the detected modulation oscillations strongly audible in a loudspeaker.

The known method of the so-called grid detection has, besides the advantage of a great sensitiveness, the disadvantage of being, with incoming powerful signals, unavoidable attended with anode detection whereby the grid detection is counteracted, and the speech or music is attenuated and distorted. With an increasing high frequency signal the triode, considered as a low frequency amplifier, begins to work on a very unfavorable part of the characteristic curve, which also gives rise to distortion.

The present invention has for its object to provide a circuit arrangement with which the advantage of grid detection remains intact, but with which undesirable anode detection issuppressed while the average potential of the control grid remains constant.

According to the invention, for this purpose, the arrangement is such that detection takes place in a circuit comprising a rectifier and a condenser, the latter being connected on one side to the non-oscillating electrode of the rectifier, and on the other side to the control grid of the amplifier. According to the invention, use should preferably be made of a thermionic rectifier which has in this case the cathode in common with the abovementioned, also thermionic, amplifier.

The invention, finally, includes a discharge tube suitable for the realization of the last mentioned circuit arrangement and comprising a cathode which slightly protrudes from the electrode complex (anode and grid or grids) 'of the amplifier and which is surrounded at this point either entirely or partly by a small auxiliary anode.

The novel features which I believe to be characteristic of my invention are set forth in particularity in the appended claims, the invention itself, however, as to both its organization and method of operation will best be understood by reference to the following description taken in connection with the drawing in which I have indicated diagrammatically several circuit organizations whereby my invention may be carried into effect.

The invention will be explained with reference to the accompanying drawing which represents, by way of example, some embodiments of the invention.

In the drawing.

Fig. 1 represents a circuit arrangement in which a triode comprising an auxiliary anode, serves for the detection and amplification,

Fig. 2 is identical to Fig. 1 with the difference that the grid circuit of the detector instead of being aperiodic is tunable,

Fig. 3 shows a pentode with an auxiliary anode, included in a circuit arrangement according to the invention,

Fig. 4 represents to an enlarged scale the stem of a detector amplifier according to the invention.

With the circuit arrangement of Fig. 1 the received modulated high frequency oscillations are made active, after being amplified, in the tuned anode circuit l of a high frequency valve which is not completely represented. With this circuit 10 l is inductively coupled a coil 2, one of the ends of which is connected to an auxiliary anode 3 of a thermionic device DA. Its other end is connected to one of the coatings of a grid condenser d. On the other side, this condenser is connected to the cathode 6 of the device DA, while across its coatings it has a leakage-resistance 5. r

The value of the condenser t is so chosen that it offers substantially no resistance to the high frequency carrier oscillations, but opposes an appreciable resistance to low frequency oscillations. The consequence thereof is that the left handcoating, consequently the one connected to the coil 2, can oscillate with a low frequency but not with a high frequency whereas the other (right hand) coating of the condenser i is connected to earth.

To the said left hand coating of, the condenser t is connected the control grid l of the thermionic device DA. This condenser, consequently, can also oscillate only with low frequency so that within the triode formed by the cathode 6, the control grid l and the anode 8, there occurs no detection but only low'frequency amplification. The detection, in the form of grid detection, entirely takes place in the circuit, 2, 3, 6, d.

A separating condenser 9, a leakage resistance It and a grid biasing battery ii are provided in order to be enabled to apply the most favorable bias potential to the control grid 1. Under certain conditions, however, the said three elements may be omitted. The further amplification of the low frequency oscillations is effected in the known manner with the aid of a transformer i2, I3, and of a final valve A comprising a cathode it, a grid I l, and an anode l'l, whereupon the oscillations are led to a reproducer 18, as phones.

The circuit arrangement represented in Fig. 2 only differs in that the tunable circuit i is directly located in the detector circuit of the valve DA. In this case it is true that both electrodes of the variable condenser of this circuit oscillate, but the electrode connected to the condenser 5 only oscillates with low frequency, ,so that there is no risk of hand capacity effect. Besides, the circuit l is directly coupled with the coil 2 of aerial I9, so that the incoming high frequency oscillations are not previously amplified. This circuit arrangement is particularly suitable for use in the neighborhood of a transmitting station. w

Such is also the case with the circuit arrangement of Fig. 3 in which the detector-amplifier DA is of the pentode power tube type and is at the same time the final valve and supplies a reproducer I8. For this purpose, the valve comprises, in addition to a control grid 1, a screen grid 20 and an auxiliary grid 2i which is connected to the middle 22 of the cathode 6. For the rest the connection is identical to that of the valve DA in Fig. 1.

Finally, Fig. 4 represents to a somewhat enlarged scale a stem of a detector amplifier valve constructed in accordance with the invention. On the front side the cathode 6, which is supposed to be an equipotential cathode, protrudes from the control grid 1 and the anode 8 to such an extent that there is some room for a small auxiliary anode 3, whose leading-in wire, which simultaneously acts as a support, is sealed into the pinch and is led out of the valve. The size of the valve consequently remains the same although now it fulfills two quite separate functions, and even is capable of setting up without any distortion considerably higher low frequency voltage variations from modulated high frequency oscillations than could be obtained with the ordinary grid detection and low frequency amplification, consequently with two separated triodes. This is due to the fact that with the circuitarrangement of the detector-amplifier according to the invention, the desired linear relation between the amplitudes of the outgoing low frequency and the incoming modulated high frequency oscillations subsists even at high values vof the latter amplitudes owing to the fact that there is no counteracting and finally dominating anode detection.

' While I have indicated and described one arrangement for carrying my invention into effect, it will be apparent to one skilled in the art that my invention is by no means limited to the particular organizations shown and described, but that many modifications may be made in the circuit arrangements, without departing from the scope of my invention as set forth in the appended claims.

What I claim is:

1. In a receiver, a combined detector-amplifier stage including a tube provided with a cathode,

' a grid, a main anode, and at least one auxiliary anode positioned outside theelectron stream between the cathode and main anode, a resonant high frequency signal input circuit connected between said auxiliary anode and said cathode providing a diode rectification network, a condenser in the low potential side of the resonant circuit connected between the auxiliary anode and the cathode, the grid being connected solely to one.

side of said condenser whereby only rectified signal energy is impressed on said grid, and an audio frequency output circuit connected between the cathode and the main anode.

2. In a receiver, a combined detector-amplifier stage including a tube provided with a cathode, a grid, a main anode, and at least one auxiliary anode positioned outside the electron stream between the cathode and main anode, a resonant high frequency signal input circuit connected between said auxiliary anode and said cathode, a condenser in the low potential side of the resonant circuit connected between the auxiliary anode and the cathode, a connection including a condenser from the grid to one side of said condenser, and an audio frequency output circuit connected between the cathode and the main anode.

3. In a receiver, a combined detector-amplifier stage including a tube provided with a cathode, a grid, a main anode, .and at least one auxiliary anode positioned outside the electron stream between the cathode and main anode, a resonant high frequency signal input circuit connected between said auxiliary anode and said cathode, a condenser in the low potential side of the resonant circuit connected between the auxiliary anode and the cathode, a connection from the grid to one side of said condenser, an audio frequency output circuit connected between the cathode and the main anode, and a negative biasing means connected between the cathode and said connection to said grid.

4. In a receiver, a combined detector-amplifier stage including a tube provided with a cathode, a grid, a main anode, and at least one auxiliary anode positioned outside the electron stream between the cathode and main anode, a resonant high frequency signal input circuit connected between said auxiliary anode and said cathode, a condenser in the low potential side of the resonant circuit connected between the auxiliary anode and the cathode, a connection including a condenser from the grid to one side of said condenser, an audio frequency output circuit connected between the cathode and the main anode, and a negative biasing means connected between the cathode and said connection to said grid.

5. In a radio receiver, the combination with a carrier wave amplifier; of a tube having a cathode, a rectifier anode, a control grid, and a,

positively polarized output anode; an input circuit for said tube upon which the carrier wave output of said amplifier is impressed; said input circuit being connected between the cathode and the rectifier anode and including, in series, a carrier-wave coupling circuit, and a resistor shunted by a carrier-wave bypass condenser; means grounding the tube cathode for audio and carrier frequencies, a coupling capacity between control grid and the junction of said resistor and carrier-wave coupling circuit; an audio frequency output circuit connected between the cathode and the positively polarized output electrode; and F means impressing between said control grid and cathode a direct current bias potential efiective to secure amplification in the audio frequency output circuit of audio frequency variations impressed upon said control grid.

6. In a radio receiver, the combination with a carrier wave amplifier, of a tube having a cathode, a control grid, a positively polarized output anode, and a, rectifier cold electrode, an input circuit for said tube upon which the carrier wave output of said amplifier is impressed, said input circuit being connected between the cathode and said rectifier electrode and including, in series, a carrier-wave coupling element and a resistor shunted by a condenser, means grounding said tube cathode, a connection between said control grid and the junction of said resistor and said coupling element for impressing the audio frequency potential component of rectified carrier waves upon said control grid, and an audio frequency output circuit connected between the said cathode and said output anode.

JAN VAN pan MARK. 

